The present invention relates to a fluid recovery system. Especially preferred embodiments of the invention are directed at a fluid recovery system for recovery of fluid by means of vacuum distillation and filtration of used lubrication oil and the like. The system of the present invention is especially advantageous as a recovery system for quenching oils, cutting oils, water soluble coolant, hydraulic oils and the like used in industrial manufacturing processes. The assignee of the present application, RPR Filtration Systems, Inc. of South Bend, Ind., has several vacuum distillation and filtering machines of the type which the present invention is related to improving, including models R/E 60 and R/E 120-B.
Common to the prior art arrangements is the utilization of the concept of distilling the fluid to be dried or cleaned in a vacuum by heating the fluid, transporting the fluid through piping to a vacuum vessel and causing the fluid to cascade downward in a vacuum chamber of the vacuum vessel where it drops to the bottom. The fluid is then transported to a separate collection vessel or recirculated through the vacuum vessel in order to increase the rate of distillation. The vacuum distillation and separation of water from petroleum oils employs the just described cycle. However, when the fluid drops to the bottom of the vacuum vessel, it is transported by a circulating pump or exit pump to a collection tank for oil which has been processed and has the water removed. Typically, the vacuum in the vacuum chamber or vessel for distillation of petroleum oils is operated in the range of 22 to 28 inches of mercury (below atmospheric pressure) where the water boils in the range of 110.degree. F. in the deepest vacuum condition to 152.degree. F. at the 22 inches of mercury vacuum condition. Especially advantageous operations of such systems according to the present invention heat the water to 180.degree. F. to facilitate volume operation.
The present invention is directed to an improved machine having a combination of features which increases the efficiency of operation, improves the ease of manufacture, eases the tasks of cleaning and removing water condensation at the upper part of the vacuum chamber, increases economization of total space required, and improves energy efficiency.
Preferred embodiments of the invention include a generally vertically extending vacuum chamber, a centrally disposed heating unit extending upwardly from the bottom of the vacuum chamber, an inlet spiral tube heat exchanger surrounding the heater assembly at the lower portion of the vacuum chamber and serving to facilitate pre-heating of the fluid to be processed before it is passed upwardly through the heater assembly, and a filter in surrounding relationship to the heater assembly for filtering out solid particles from the fluid as it is flowed outwardly from the top of the heating assembly and cascaded downwardly toward the bottom of the vacuum chamber. This overall combination results in an efficient use of space as well as economies of manufacture and conservation of energy.
In especially preferred embodiments, the filter arrangement is a cylindrical unit surrounding the correspondingly cylindrical heater unit at the center of the vacuum vessel. The filter can thus be easily changed and/or cleaned by simply removing the top cover of the vacuum chamber to gain access thereto.
Since the inlet coils for the fluid to be processed extend concentrically around the lower portion of the heater unit below the filter section and are immersed in the oil that has cascaded downwardly to the bottom of the vacuum chamber, both a pre-warming of the inlet oil and a pre-cooling of the processed oil is automatically and efficiently effected. In this connection, the processed oil which collects at the bottom of the chamber is advantageously cooled by the incoming oil so that this processed oil can be more readily immediately used for lubrication or other purposes than would be the case if it remained in its maximally heated condition.
By arranging the heater assembly as insertable from the bottom of the vacuum chamber, it can be readily installed and removed as a unit with a minimum of manufacturing expense. The cylindrical heating unit includes a tubular enclosure, inside of which are a plurality of vertically extending heating elements, the tubular enclosure accommodating the flow of the fluid to be treated from the bottom thereof upwardly through the tubular heating enclosure to outlet openings inside of the space surrounded by the filter adjacent the upper end of the vacuum chamber.
According to especially preferred embodiments of the invention, the fluid level at the bottom of the vacuum chamber vessel is controlled by dual floats, the lower float regulating the lowest point of the fluid level, the higher float monitoring the upper fluid level. Preferably, these floats are disposed externally to the vacuum chamber casing for ease of maintenance and assembly. The high float controls the inflow of fluid to the vacuum vessel and the lower float controls the outflow. The floats are preferably controlled by time circuits, by mechanical timing, or electronic timing. There may be delays so as to avoid rapid cycling of inflow or outflow devices, according to especially preferred embodiments.
An important feature of preferred embodiments of the present invention is the construction of a removable cover and seal for the vacuum chamber vessel. According to the invention, the upper edge of the vacuum chamber vessel is provided with a radially inwardly projecting offset for accommodating a seal in the form of an O-ring. The dome-shaped cover, which includes a fitting at the upper portion for connecting to the vacuum pump, is provided with a diameter corresponding to a diameter of the vacuum chamber vessel. The offset is so configured that the O-ring rests in place on top of the offset and when a vacuum is applied, the O-ring is drawn tightly to the tank top without requiring other fastening mechanisms. This arrangement has the distinct advantage of automatically accommodating for the experienced condensation of water vapors at the top cover of the vacuum vessel when the vacuum pumping is terminated. With conventional constructions, the moisture collects in droplets of water which travel by gravity down the side of the dome and the side of the tank into the fluid or oil which has already been processed. With the offset configuration of the present invention, the condensation collects at this offset, since the offset collects the water as it travels down the lower portion of the dome and prevents it from going further downwardly into the sidewalls of the vacuum vessel. This minimizes the amount of contamination by this condensation phenomena.
Another important feature of certain preferred embodiments of the invention is the provision of a sensor for controlling the heat in the heating vessel, which sensor extends from the bottom of the vessel through the centrally disposed heater and up into a position at the point of the heating unit where the fluid being processed exits the heater and enters the evacuated vacuum chamber space. With this arrangement the thermostat sensor is most sensitive to the critical temperatures at which the water is boiled off from the oil. Also, the sensor is sensitive to conditions of operations without fluid, whereby the sensor detects this condition immediately and turns the heater off, and thus avoids overheating. Similarly, when the fluid in the heating vessel may not be circulating, the same relationship occurs and the sensor would immediately detect same and appropriately control the heating unit.
With the arrangement of the heat exchanger and heating unit centrally of the vacuum chamber vessel, there is an improvement in operating efficiencies due to a reduction in heat losses through various stages and due to optimum heat exchange. Furthermore, the total space required for the machine is substantially reduced as compared with machines having different housing for the filter/heat exchanger/heating unit.
In particularly preferred embodiments a further temperature sensor is provided at the vacuum outlet line from the vacuum chamber, which further sensor effectively detects the level of dryness of the oil because the vapor temperature drops as the water content is reduced. This further sensor is operatively connected to shut down the machine when the desired dehydration has been reached. For start-up operations a manual bypass switch is provided to ensure that the machine first reaches operating temperatures at the vapor outlet.
Other objects, advantages, and novel features of the present invention will become apparent from the following detailed description of the single embodiment, when considered in conjunction with the accompanying drawing.